It's in the cards.
Putin was propping it up. However, Assad has been unable to contain the rebellion and now, has become an embarrassment. Thus Putin, never one to concern himself with the fortunes of people he is not personally engaged with, is now playing the humanitarian argument as an exit card.
Assad will probably go down ******-style: to the last breath and only after firing his very last bullet. He won't be the butcher Saddam was: chemical weapons are just too ghastly for a politician such as he. No, he'll just succumb to his own "human weakness" and unleash a canister of biological agents in one -- or two -- of those restive provinces. That'll be the catalyst for a massive aerial bombardment on Syria's military, which may well result in Assad's demise.
It's highly probable he'll be assassinated before it gets to that, however.